The present invention concerns a method for coordinating elevator group traffic in buildings with one or more change levels constituting one of the end stations for the elevator groups operating above and below the change level.
In tall buildings, especially in skyscrapers housing office premises, the elevator groups are usually arranged in zones so that the elevators in a given zone only serve calls within that zone, the zones being arranged one above the other, which means that it is only possible to reach a given floor by using an elevator that operates within the zone concerned. The zones not served by a given elevator and passed without stopping are called express zones. The purpose of this arrangement is to maximize the transportation capacity of the elevator system during the morning and afternoon rush hours. The elevator groups in the different zones are usually controlled by a conventional automatic and independent group control system, such as those presented e.g. in U.S. Pat. Nos. 4,567,560 and 4,582,173.
Regarding elevator traffic arrangements, very tall buildings with more than 50 floors are preferably divided into two or more sections in the vertical direction. The lower section up to the change level ("sky lobby") is served by an elevator system divided into zones as described above, and the upper section by another such system. The sky lobby is reached directly from the ground floor by means of shuttle elevators. In this way a larger transportation capacity is achieved for the elevator shaft volume available, i.e. the ratio of the horizontal sectional area of the building to the space required by the elevators is better. However, this system has the drawback that it involves increased travelling times, due to the necessity of changing elevators at the sky lobby. As there is a very strong need for reducing the area of the elevator shaft, this has resulted in the introduction of the double-deck elevator to increase the transportation capacity. In this solution, one of the two cars is mounted on top of the other. The elevator stops at every second floor. If the passenger is on the "wrong" floor, he has to get to the floor above or below either before or after the drive, e.g. using an escalator. This system has the drawback of being unpractical and causing extra traffic between even and odd floors, especially in communities covering several floors. In estimating the performance of an elevator group, the following three questions should be considered (see Committee 2A "Vertical and Horizontal Transportation", of the Council of Tall Buildings and Urban Habitat, Part of the Monograph of the Planning and Design of Tall Buildings, chap. SC-4, pages 139-140):
Transportation capacity, expressed as a percentage of the total number of people in the building during the two five-minute periods (morning and afternoon rush hours) during which the elevators are most heavily loaded,
Average time interval between the arrivals of elevators at a typical floor level,
Longest travelling time in the up direction.
Typical values for these quantities in a first-class office building, according to the same source, are: transportation capacity 11-13%, average interval between arrivals 25-35 s, and max. travelling time 180 s. These values apply for a diversified building accommodating several enterprises. In single-purpose buildings the corresponding values are typically somewhat better.
In the elevator systems used today, the main problems are the waiting times, which may be unduly long during peak traffic, about 2-3 times longer than the average interval between elevator arrivals, which is rather too much particularly for people who have to change elevators in buildings with a sky-lobby. Such waiting times therefore constitute a deterioration of the performance of the elevator system, at least with regard to the last-mentioned criterion. Moreover, it is obvious that a reduction in the waiting times will involve indirect improvements in the performance of the system with regard to other criteria as well. It seems fairly unlikely that any substantial improvements could be achieved in today's elevator systems based on independent group control.